Polycarboxylic acids have many uses as chemical intermediates or monomers for industrial production of nylons, plastics, and many other industrial polymers. At present, the vast majority of polycarboxylic acid monomers are produced from petroleum. Recently, it has become possible to utilize genetically engineered microorganisms to produce polycarboxylic acids at an industrial scale using carbon sources other than petroleum such as various sugars, fats and oils. The engineered microorganisms can be cultured in a suitable liquid medium containing a carbon source or sources as well as other required nutrients. When cultured under desirable temperature, pH, dissolved oxygen and the like, the microorganisms can produce and secrete the polycarboxylic acids into the culture medium. The polycarboxylic acids can then be separated from this medium and purified to the extent necessary for use in particular industrial processes.